<?php

namespace Aws\Sts\RegionalEndpoints;

use Aws\AbstractConfigurationProvider;
use Aws\CacheInterface;
use Aws\ConfigurationProviderInterface;
use Aws\Sts\RegionalEndpoints\Exception\ConfigurationException;
use GuzzleHttp\Promise;
use GuzzleHttp\Promise\PromiseInterface;

/**
 * A configuration provider is a function that returns a promise that is
 * fulfilled with a {@see \Aws\Sts\RegionalEndpoints\ConfigurationInterface}
 * or rejected with an {@see \Aws\Sts\RegionalEndpoints\Exception\ConfigurationException}.
 *
 * <code>
 * use Aws\Sts\RegionalEndpoints\ConfigurationProvider;
 * $provider = ConfigurationProvider::defaultProvider();
 * // Returns a ConfigurationInterface or throws.
 * $config = $provider()->wait();
 * </code>
 *
 * Configuration providers can be composed to create configuration using
 * conditional logic that can create different configurations in different
 * environments. You can compose multiple providers into a single provider using
 * {@see \Aws\Sts\RegionalEndpoints\ConfigurationProvider::chain}. This function
 * accepts providers as variadic arguments and returns a new function that will
 * invoke each provider until a successful configuration is returned.
 *
 * <code>
 * // First try an INI file at this location.
 * $a = ConfigurationProvider::ini(null, '/path/to/file.ini');
 * // Then try an INI file at this location.
 * $b = ConfigurationProvider::ini(null, '/path/to/other-file.ini');
 * // Then try loading from environment variables.
 * $c = ConfigurationProvider::env();
 * // Combine the three providers together.
 * $composed = ConfigurationProvider::chain($a, $b, $c);
 * // Returns a promise that is fulfilled with a configuration or throws.
 * $promise = $composed();
 * // Wait on the configuration to resolve.
 * $config = $promise->wait();
 * </code>
 */
class ConfigurationProvider extends AbstractConfigurationProvider
	implements ConfigurationProviderInterface {
	const DEFAULT_ENDPOINTS_TYPE = 'legacy';
	const ENV_ENDPOINTS_TYPE = 'AWS_STS_REGIONAL_ENDPOINTS';
	const ENV_PROFILE = 'AWS_PROFILE';
	const INI_ENDPOINTS_TYPE = 'sts_regional_endpoints';

	public static $cacheKey = 'aws_sts_regional_endpoints_config';

	protected static $interfaceClass = ConfigurationInterface::class;
	protected static $exceptionClass = ConfigurationException::class;

	/**
	 * Create a default config provider that first checks for environment
	 * variables, then checks for a specified profile in the environment-defined
	 * config file location (env variable is 'AWS_CONFIG_FILE', file location
	 * defaults to ~/.aws/config), then checks for the "default" profile in the
	 * environment-defined config file location, and failing those uses a default
	 * fallback set of configuration options.
	 *
	 * This provider is automatically wrapped in a memoize function that caches
	 * previously provided config options.
	 *
	 * @param array $config
	 *
	 * @return callable
	 */
	public static function defaultProvider(array $config = []) {
		$configProviders = [self::env()];
		if(
			!isset($config['use_aws_shared_config_files'])
			|| $config['use_aws_shared_config_files'] != false
		) {
			$configProviders[] = self::ini();
		}
		$configProviders[] = self::fallback();

		$memo = self::memoize(
			call_user_func_array([ConfigurationProvider::class, 'chain'], $configProviders)
		);

		if(isset($config['sts_regional_endpoints'])
			&& $config['sts_regional_endpoints'] instanceof CacheInterface
		) {
			return self::cache($memo, $config['sts_regional_endpoints'], self::$cacheKey);
		}

		return $memo;
	}

	/**
	 * Provider that creates config from environment variables.
	 *
	 * @return callable
	 */
	public static function env() {
		return function() {
			// Use config from environment variables, if available
			$endpointsType = getenv(self::ENV_ENDPOINTS_TYPE);
			if(!empty($endpointsType)) {
				return Promise\Create::promiseFor(
					new Configuration($endpointsType)
				);
			}

			return self::reject('Could not find environment variable config'
				.' in '.self::ENV_ENDPOINTS_TYPE);
		};
	}

	/**
	 * Fallback config options when other sources are not set.
	 *
	 * @return callable
	 */
	public static function fallback() {
		return function() {
			return Promise\Create::promiseFor(
				new Configuration(self::DEFAULT_ENDPOINTS_TYPE, true)
			);
		};
	}

	/**
	 * Config provider that creates config using a config file whose location
	 * is specified by an environment variable 'AWS_CONFIG_FILE', defaulting to
	 * ~/.aws/config if not specified
	 *
	 * @param string|null $profile Profile to use. If not specified will use
	 *                              the "default" profile.
	 * @param string|null $filename If provided, uses a custom filename rather
	 *                              than looking in the default directory.
	 *
	 * @return callable
	 */
	public static function ini(
		$profile = null,
		$filename = null
	) {
		$filename = $filename ?: (self::getDefaultConfigFilename());
		$profile = $profile ?: (getenv(self::ENV_PROFILE) ?: 'default');

		return function() use ($profile, $filename) {
			if(!@is_readable($filename)) {
				return self::reject("Cannot read configuration from $filename");
			}
			$data = \Aws\parse_ini_file($filename, true);
			if($data === false) {
				return self::reject("Invalid config file: $filename");
			}
			if(!isset($data[$profile])) {
				return self::reject("'$profile' not found in config file");
			}
			if(!isset($data[$profile][self::INI_ENDPOINTS_TYPE])) {
				return self::reject("Required STS regional endpoints config values
                    not present in INI profile '{$profile}' ({$filename})");
			}

			return Promise\Create::promiseFor(
				new Configuration($data[$profile][self::INI_ENDPOINTS_TYPE])
			);
		};
	}

	/**
	 * Unwraps a configuration object in whatever valid form it is in,
	 * always returning a ConfigurationInterface object.
	 *
	 * @param mixed $config
	 * @return ConfigurationInterface
	 * @throws \InvalidArgumentException
	 */
	public static function unwrap($config) {
		if(is_callable($config)) {
			$config = $config();
		}
		if($config instanceof PromiseInterface) {
			$config = $config->wait();
		}
		if($config instanceof ConfigurationInterface) {
			return $config;
		}
		if(is_string($config)) {
			return new Configuration($config);
		}
		if(is_array($config) && isset($config['endpoints_type'])) {
			return new Configuration($config['endpoints_type']);
		}

		throw new \InvalidArgumentException('Not a valid STS regional endpoints '
			.'configuration argument.');
	}
}
